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122 lines
2.8 KiB
C++
122 lines
2.8 KiB
C++
#include <queue>
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#include <vector>
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#include <climits>
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#include <iostream>
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using namespace std;
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typedef long long ll;
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typedef pair<int, int> pii;
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const int maxnodes = 200000;
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int nodes = maxnodes;
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int prio[maxnodes], curflow[maxnodes], prevedge[maxnodes], prevnode[maxnodes], q[maxnodes], pot[maxnodes];
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bool inqueue[maxnodes];
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struct Edge {
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int to, f, cap, cost, rev;
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};
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vector<Edge> graph[maxnodes];
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void addEdge(int s, int t, int cap, int cost) {
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Edge a = {t, 0, cap, cost, graph[t].size()};
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Edge b = {s, 0, 0, -cost, graph[s].size()};
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graph[s].push_back(a);
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graph[t].push_back(b);
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}
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void bellmanFord(int s, int dist[]) {
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fill(dist, dist + nodes, INT_MAX);
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dist[s] = 0;
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int qt = 0;
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q[qt++] = s;
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for (int qh = 0; (qh - qt) % nodes != 0; qh++) {
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int u = q[qh % nodes];
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inqueue[u] = false;
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for (int i = 0; i < (int) graph[u].size(); i++) {
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Edge &e = graph[u][i];
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if (e.cap <= e.f) continue;
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int v = e.to;
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int ndist = dist[u] + e.cost;
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if (dist[v] > ndist) {
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dist[v] = ndist;
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if (!inqueue[v]) {
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inqueue[v] = true;
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q[qt++ % nodes] = v;
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}
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}
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}
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}
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}
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pii minCostFlow(int s, int t, int maxf) {
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// bellmanFord can be safely commented if edges costs are non-negative
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bellmanFord(s, pot);
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int flow = 0;
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int flowCost = 0;
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while (flow < maxf) {
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priority_queue<ll, vector<ll>, greater<ll> > q;
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q.push(s);
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fill(prio, prio + nodes, INT_MAX);
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prio[s] = 0;
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curflow[s] = INT_MAX;
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while (!q.empty()) {
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ll cur = q.top();
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int d = cur >> 32;
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int u = cur;
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q.pop();
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if (d != prio[u])
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continue;
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for (int i = 0; i < (int) graph[u].size(); i++) {
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Edge &e = graph[u][i];
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int v = e.to;
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if (e.cap <= e.f) continue;
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int nprio = prio[u] + e.cost + pot[u] - pot[v];
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if (prio[v] > nprio) {
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prio[v] = nprio;
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q.push(((ll) nprio << 32) + v);
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prevnode[v] = u;
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prevedge[v] = i;
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curflow[v] = min(curflow[u], e.cap - e.f);
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}
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}
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}
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if (prio[t] == INT_MAX)
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break;
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for (int i = 0; i < nodes; i++)
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pot[i] += prio[i];
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int df = min(curflow[t], maxf - flow);
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flow += df;
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for (int v = t; v != s; v = prevnode[v]) {
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Edge &e = graph[prevnode[v]][prevedge[v]];
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e.f += df;
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graph[v][e.rev].f -= df;
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flowCost += df * e.cost;
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}
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}
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return make_pair(flow, flowCost);
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}
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// Usage example
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int main() {
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int capacity[3][3] = {
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{ 0, 3, 2},
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{ 0, 0, 2},
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{ 0, 0, 0}
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};
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nodes = 3;
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for (int i = 0; i < nodes; i++)
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for (int j = 0; j < nodes; j++)
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if (capacity[i][j] != 0)
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addEdge(i, j, capacity[i][j], 1);
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int s = 0;
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int t = 2;
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pii res = minCostFlow(s, t, INT_MAX);
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int flow = res.first;
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int flowCost = res.second;
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cout << (4 == flow) << endl;
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cout << (6 == flowCost) << endl;
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}
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